It's hard to say that anything's impossible, of course, except things made so by definition or by being contrary to observational facts, but the best work shows that intra-atomic energy is just about as impossible as anything can well be.

Dropping her unceremoniously to the floor he stared through the telescope sight of an enormous ray-generator which had automatically aligned itself upon the distant point of liberation of intra-atomic energy which had caused the alarm to sound.

Whereas he had worked with intra-atomic energy schoolboy fashion, the master craftsman before him knew every reagent, every reaction, and worked with known and thoroughly familiar agencies to bring about his exactly predetermined ends -- just as calmly certain of the results as Seaton himself would have been in his own laboratory, mixing equivalent quantities of solutions of barium chloride and of sulphuric acid to obtain a precipitate of barium sulphate.

As she proceeded, however, the warnings of the liberation of intra-atomic energy grew stronger and stronger, and both men scanned their path intensely for a sight of the source of the disturbance, while their velocity was cut to only a few hundred miles an hour.